Personally I use the trainer for every type of workout that I would do on the road when outdoor riding is a no go. I have a few Spinnerval workouts that I do. I try to match the effort that I would expend on the road with heart rate, power and cadence. Boredom isn't not too much of an issue for me as long as I'm doing a structured workout. Don't get me wrong the trainer is a distant second to real world riding but it beats not riding. I max out around three hours or 50 pseudo miles. It's also good when coming back from an illness or injury and you want to see what you've got before you take it outside.
In case you don't already know it the trainer will eat up your tire in short order and you should replace the skewer in the rear wheel with one dedicated for the trainer. The stress of holding the bike on the trainer can damage the skewer so most trainers come with a steel skewer for that purpose. I have a dedicated wheel that I swap out for that purpose with the same cassette as my road wheel and an indoor trainer tire. Makes the set up quick and simple. I don't want to give myself any excuses to skip the workout.